RIASSUNTO
The actual and potential impacts of increased pollutant concentrations bring great pressures to the health of the aquaculture ecosystem. The paper attempts to outline conceptual models that can illustrate the links between the threats and the marine aquaculture ecosystem and to select suitable indicators, which can reflect the health state of the ecosystem. The models turn out that human activities, self-pollution, chemical abuse and climate changes etc. have been the most serious threats. It is also concluded that not only physical-chemical conditions and biological indicators but also economy (social) components can influence the aquaculture ecosystem health. And finally, as a reflection of the overall aquaculture ecosystem condition, aquaculture environment carrying capacity has been taken as an important indicator.
INTRODUCTION
The concept of ecosystem health can be found in the writing of Aldo Leopold. He recognized that not only individuals, but also whole ecosystems could show signs of disease or sickness as a result of stress from human activities. Costanza et al. (1992) defined ecosystem health as follows: an ecological ecosystem is health and free from ''distress syndrome'' if it is stable and sustainable. Rapport (1994) considered that ecosystem health should be a systematic concept. It seeks to understand and optimize the intrinsic capacity of an ecosystem for self-renewal while meeting reasonable human goals. It encompasses the role of societal values, attitudes and goals in shaping our conception of health at human and ecosystem scales. Presently, there is a veritable industry boom around the development of indicators of ecosystem health. Indeed, a variety of indicators are now being evaluated to assess how well they depict the health of managed ecosystems. Some conceptual framework or models for evaluating the health of major ecosystem types such as coastal areas, forests, wetland, estuaries, and lakes have been developed (John, 1993; Xu, 2004; Felix, 2006; Qi, 2007; Haynes, 2007).